When the surface of the above-mentioned long piece of material is processed by using a cutting tool, a cutting wheel, a brush, a belt sander, etc., especially when the material is a wire rod with a small cross section, it is very difficult to continuously and uniformly cut its periphery. For this reason, the oxide scale or rust on a wire rod is removed by washing it out with acid or is peeled by using a die or the like (for example, see JP No. 28-57279), and extraneous matter is removed by washing it out with alkali or organic solvent.
However, there were problems in that when acid is used for the washing, the use of a lot of water that is needed as an environmental countermeasure to process the waste water results in an expensive large-scale equipment; when processing thin wire rods, they tend to mutually contact and thus it is difficult to uniformly dip and process the entire wire rod; and when a long piece of material of iron is processed, its mechanical quality could be reduced depending on the used acid (chemicals). When once the washing operation by acid water in the above-mentioned large-scale equipment is interrupted, the long piece of material being processed tends to be excessively dipped in acid so that its surface could severely be deteriorated. Thus, it was difficult to realize an in-line large-scale processing apparatus for washing by acid.
There have been harmful effects in that when extraneous matter is removed by having a long piece of material pass between cutting tools such as a composite blade or die, a trace of cutting tools remains on the long piece of material or a thin wire rod is cut due to tension caused by cutting resistance.
There have been problems in that when a material is washed by alkali or organic solvent, it is very troublesome to manage chemical solutions used similarly to washing by acid in terms of protection against the working environment, and in that a large-scale apparatus is also inevitable for the wet method.